The present invention relates to an ink composition, more particularly to a water-soluble magenta ink composition for ink-jet recording, which contains an anthrapyridone disulfonic acid compound or the salt thereof as the colorant having a wide range of blend color and an excellent property in color tone, light fastness and water fastness; an ink-jet recording method using said composition; an water-based magenta dye comprising said disulfonic acid compound or the salt thereof having a low content of inorganic salt; and a method for producing said disulfonic acid compound or the salt thereof having a low content of said inorganic salt.
Diverse ink jetting processes have been developed for the recording method by ink-jet printer, and each method comprises the process of generating ink droplets and then depositing them onto various recording materials (such as paper, film, cloth). The recording method by means of ink-jet printer has rapidly been spread in recent years and will be propagated in future because the method makes no noise due to the system in which a recording head does not contact with the recording material and because the method advantageously allows the printer easily to be downsized, to work in a high-speed and to give color printing. In order to record in color an image information or a character information on a computer color display by an ink-jet printer, it is generally printed to by subtractive color mixing of four colored-inks, namely yellow, magenta, cyan and black. In order to reproduce an image pictured by additive color mixing of R, G ,B on a CRT display as identical as possible by subtractive color mixing, the dyes used therefor, especially for a YMC ink, are desired to have color hues close to the respective standards of YMC (xe2x80x9cJapan Color Standard Paperxe2x80x9d published by Japan Printing Machinery Manufacturers Association)and vividness. Additionally, it is required that the resulting ink composition is stable for long-term storage and that the resulting printed image is of a high optical density and has excellent fastness including water fastness and light fastness. The present invention relates to a magenta ink.
The use of ink-jet printers are enlarged from a small-sized one for OA to a big-sized one for industrial use. So, there arise a keen demand more than ever on fastness such as water fastness and light fastness of the printed image. The water fastness is substantially improved by coating inorganic or organic micro particles such as cationic polymer(not an inorganic particle), porous silica, alumina sol and special ceramics which can absorb dye from ink with PVA resin on a paper sheet. Various coated sheets for ink-jet printing are already available on the market, but they can not always give a satisfactory water fastness. Light fastness is not yet improved by an established technique. Especially, the majority of magenta dyes, one of four original colors of YMCK, are poor in light fastness, and its improvement is an important problem to be solved.
The chemical skeletal structure of magenta dyes used in a water-soluble ink for ink-jet recording is represented by a xanthene type disclosed by JP Laid-Open No.89811/1979, JP Laid-Open No.60053/1996 and JP Laid-Open No.143798/1996, or an azo type using the H acid disclosed by JP Laid-Open No.62562/1986, JP Laid-Open No.156168/1987, JP Laid-Open No.203970/1991, JP Laid-Open No.157698/1995 and JP Publication No.78190/1995. The xanthene type is indeed excellent in hue and vividness, but is inferior in light fastness. The azo type using the H acid is good in hue and water fastness, but is inferior in light fastness and vividness. As disclosed by JP Laid-Open No.203970/1991, for example, some magenta dyes excellent in vividness and light fastness have been developed from the azo type family, but are still inferior in light fastness to the other hue of dyes such as yellow dyes and cyan dyes represented by copper phthalocyanine type.
For a chemical skeletal structure of magenta dyes excellent in vividness and light fastness, an anthrapyridone type is known as disclosed by JP Laid-Open No.195775/1982, JP Laid-Open No.74173/1984 and JP Laid-Open No.16171/1990, but is not yet able to satisfy all of the properties in a wide range of blend color, hue, vividness, light fastness, water fastness and stability in solution. The U.S. Pat. No. 2,644,821 discribes an anthrapyridone type compound including the compound of below Formula (2) and its disulfonic acid compound as a good light fastness and water fastness of dye, but they are intended to use mainly for fiber-dyeing and can not show a high quality suitable for an ink-jetting ink, if used directly with no additional procedures.
An object of the present invention is to provide a water-based magenta ink composition which has a wide range of blend color in hue and vividness suitable for ink-jet recording and gives the recorded material a high fastness in light fastness and water fastness; and a magenta dye suitable therefor.
The present inventors made a diligent study to solve the above problem and, as a result, have completed the present invention. Namely, the present invention is as follows:
(1) A water-based magenta ink composition, which comprises the disulfonic acid derivative of a compound represented by Formula(2) or the salt thereof as the dye component. 
(2) A water-based magenta ink composition according to the above term (1), wherein said disulfonic acid derivative of a compound represented by Formula(2) is 85% or more (area ratio according to high performance liquid chromatography(HPLC)) in content and a monosulfonic acid compound of the compound represented by Formula(2) according to the above terms (1) is 10% or less(area ratio according to HPLC)in content.
(3) A water-based magenta ink composition according to the above term (1) or (2), wherein said disulfonic acid compound is a compound (or the salt thereof, hereinafter likewise) represented by Formula(1). 
(4) A water-based magenta ink composition according to any of the above terms (1) to (3), wherein said composition contains water and an organic solvent.
(5) A water-based magenta ink composition according to any of the above terms (1) to (4), wherein an inorganic salt in said dye component is 1% or less in content.
(6) A water-based magenta ink composition according to any of the above terms (1) to (5), wherein said composition is for ink-jet recording.
(7) A method for ink-jet recording, which comprises using the water-based magenta ink composition according to any of the above terms (1) to (5) for an ink in the ink-jet recording way that ink droplets are jetted responding to recording signals to record on a recording material.
(8) A method for ink-jet recording, which comprises using the water-based magenta ink composition according to any of the above terms (1) to (5) for a magenta ink, and using a water-based cyan ink containing a water-soluble metal phthalocyanine dye for a cyan ink in the ink-jet recording way that ink droplets are jetted responding to recording signals to record on a recording material.
(9) A method for ink-jet recording according to the term (8), wherein said recording material is a polyamide fiber material, which is thermally treated after jetting said ink composition.
(10) A method for ink-jet recording according to the term (8), wherein said recording material is a sheet for information transmitting.
(11) A method for ink-jet recording according to the term (10), wherein said sheet for information transmitting is a surface-treated sheet.
(12) An ink-jet printer, which comprises being equipped with a container storing the water-based magenta ink composition according to any of the above terms (1) to (5) and a container storing the water-based cyan ink containing a water-soluble metal phthalocyanine dye.
(13) A dye for water-based magenta ink, which comprises containing the disulfonic acid compound represented by Formula(1) or the salt thereof by 90% or more(area ratio according to HPLC), the monosulfonated product (monosulfonic acid compound) of the compound represented by Formula(2) by 5% or less(area ratio according to HPLC), and the inorganic salt by 1% or less.
(14) A method for producing the disulfonic acid compound represented by Formula (1) or the salt thereof, which comprises disulfonating the anthrapyridone compound represented by Formula (2) with fuming sulfuric acid, salting out conventionally the disulfonic acid compound thus obtained to give a wet cake, and then treating the wet cake with a hydrous lower alcohol.